Short Circuit Evaluation in Go

In programming, short circuit evaluation is a technique where an expression is only evaluated if it is necessary to determine the result of the surrounding statement. This is often used in conditional statements, where the evaluation of multiple conditions is unnecessary if an earlier condition is already false.

Go implements short circuit evaluation for logical operators (&& and ||), similar to many other programming languages. This means that in an if statement, the interpreter will evaluate the conditions from left to right and stop as soon as the result is known.

Regarding the provided code examples, the evaluation order of the conditions does not affect the performance of the program. In Go, both code snippets will behave the same way. The compiler will evaluate the expressions from left to right and short-circuit the evaluation as soon as it determines the outcome.

To demonstrate this, consider the following code:

package main

import "fmt"

func main() {
    var r *http.Request
    queries := make(map[string][]string)

    if r == nil || len(queries) == 0 || !isValidQueryParams(&queries) {
        fmt.Println("Invalid querystring")
    }
}

Even though isValidQueryParams has more overhead than r == nil and len(queries) == 0, the compiler will evaluate the expressions in order and short-circuit as soon as the result is clear. Therefore, there is no performance difference between the two code snippets in your example.